linux-kernel - Re: [PATCH 4/4] tty: n_gsm: fix missing corner cases in gsmld

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Date:   Thu, 7 Jul 2022 08:48:35 +0200
From:   Jiri Slaby <jirislaby@...nel.org>
To:     "D. Starke" <daniel.starke@...mens.com>,
        linux-serial@...r.kernel.org, gregkh@...uxfoundation.org
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] tty: n_gsm: fix missing corner cases in gsmld_poll()

On 06. 07. 22, 7:44, D. Starke wrote:
> From: Daniel Starke <daniel.starke@...mens.com>
> 
> gsmld_poll() currently fails to handle some corner cases correctly:
> - tty ldisc association lost
> - remote party closed the associated tty
> 
> Add the missing checks and map those to EPOLLHUP.
> Reorder the checks to group them by their reaction.
> 
> Fixes: e1eaea46bb40 ("tty: n_gsm line discipline")
> Signed-off-by: Daniel Starke <daniel.starke@...mens.com>
> ---
>   drivers/tty/n_gsm.c | 10 ++++++++--
>   1 file changed, 8 insertions(+), 2 deletions(-)
> 
> Based on tty-testing.
> 
> diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
> index 51447ccccbab..47566bd2ed6e 100644
> --- a/drivers/tty/n_gsm.c
> +++ b/drivers/tty/n_gsm.c
> @@ -3051,14 +3051,20 @@ static __poll_t gsmld_poll(struct tty_struct *tty, struct file *file,
>   	__poll_t mask = 0;
>   	struct gsm_mux *gsm = tty->disc_data;
>   
> +	if (!gsm)
> +		return EPOLLHUP;

Hmm, how can this happen? It's a tty bug if it calls ld ops after 
NULLing disc_data.

thanks,
-- 
js
suse labs